Jarda, This is excellent! I'm really enjoying watching the progress on this project. I was wondering about the black primer and then I realised what you meant by it. The white plastic is opaque and if you paint it white the light shines through, so you loose all the definition and detail and it looks odd. Thanks for posting.
Michael, The small compressor at the front left hand side of the block is the air con compressor. Below is a couple of 8V71T Detroit's that I built from the AMT T500 Peterbilt 359 and the AMT 352 Pacemaker. The kit engines are standard supercharged, I just added a turbo charger to both. The engine on the left is for a future build 359 and the engine on the right, is as Peterbilt would have had the engine configured for installation in the pacemaker. They would normally paint their engines white but I kept them Detroit Alpine Green. Hope this helps.
Michael, See if you can get hold of a Peterbilt owners maintenance manual for a 359 from the late 60s (They came in red cover). I have one here that covers a 351, 352, 358. It has all the wiring and air line diagrams in the back. These cover both straight trucks with trailer connections and also tractor semi trucks. Hope this helps. Best Regards Dave